This invention relates to an improved composition for removing water and residual aqueous leak tracer solutions used in locating leaks in fuel tanks, particularly in aircraft, and is especially concerned with an improved "depuddling" agent, which is miscible with both a water-based solution used for detecting or tracing leaks in fuel tanks, and with the oil-based fuel employed in such tanks, and which can be readily employed for removing residual leak tracer solution from the fuel tanks prior to introduction of the main body of fuel into the tanks. The invention also concerns procedure for employing such "depuddling" agent for removing residual leak tracer solution from fuel tanks.
In my copending application Ser. No. 66,609, filed Aug. 15, 1979, there is disclosed and claimed leak tracer solutions particularly effective for inspection of aircraft fuel tanks and lines prior to use, consisting essentially of water, a nonionic oxyalkylated aliphatic alcohol surfactant, and a small amount of a dye which is essentially non-staining on painted surfaces. The leak tracer solution is introduced into the fuel tank system, and following inspection for leaks in the system, generally the leak tracer solution is drained from the fuel tanks and lines. However, problems of entrapment of the leak tracer solution in components of the fuel system arise, since the fuel which is then introduced into the fuel tanks is oil-based, such as a hydrocarbon, and is not miscible with the water-based leak tracer. Accordingly, the residual leak tracer solution, e.g. in crevices or corners of the fuel tank system, and in low portions of fuel lines, remains entrapped therein and is not removed.
It is accordingly an object of the present invention to provide a composition or liquid which can be employed to "bridge" or "couple" a water-based solution such as the above noted leak tracer solution, with an oil-based liquid, such as the hydrocarbon fuel of an aircraft. Another object of the invention is the provision of a composition or solution having the above characteristics, and hereinafter termed a "depuddling" agent, which is miscible with an aqueous leak tracer solution employed for detection of leaks in fuel tank systems, and with the oil-based fuel employed in such tank system, so that the depuddling agent forms a solution with any residual leak tracer solution, and the resulting mixture or solution forms another solution with the oil-based fuel, so that the final mixture can be readily removed from the fuel tank system. A still further object is the provision of procedure for removing residual or trace amounts of leak tracer solutions from fuel tank systems, employing the above compositions or dupuddling agents.
U.S. Pat. No. 4,035,641 discloses a liquid oxygen compatible dye penetrant composition which comprises an oxyalkylated aliphatic alcohol nonionic surfactant, a small amount of a dye soluble in such surfactant, and a major proportion of a non-halogenated organic solvent, such as a saturated aliphatic hydrocarbon, e.g. containing from about 5 to about 8 carbon atoms.
In my copending application, Ser. No. 925,497, filed July 17, 1978, there is disclosed and claimed a liquid dye penetrant composition, comprising an oxyalkylated aliphatic alcohol non-ionic surfactant, a dye soluble therein, and an isoparaffinic solvent extender consisting essentially of isoparaffins.